A method for preparing a highly resistant circulating water-based aluminum pigment and the prepared highly resistant circulating water-based aluminum pigment and application thereof

Abstract

The invention discloses a method for preparing a highly resistant circulating water-based aluminum pigment, relates to the technical field of chemical materials, and aims to improve the resistant circulating performance of the aluminum pigment, comprising the following steps: adding a silver dollar type aluminum pigment slurry to a double-jacketed reactor, dispersing with isopropanol, and stirring to obtain an aluminum pigment suspension; coating the surface of the aluminum pigment with a flexible organic polymer; and then coating with a rigid silane coupling agent for a second time. The invention also discloses a highly resistant circulating water-based aluminum pigment prepared by the above method and its application in automatic spraying water-based automotive coatings. The invention adopts a double-layer or even multi-layer coating system, wherein the inner layer is coated with a flexible organic polymer such as polyvinyl butyral to coat the aluminum pigment core, and the outer layer is coated with a rigid silane coupling agent, wherein the inner layer provides a buffer, and the outer layer enhances protection, and the two act synergistically, and the prepared pigment has high degassing stability and mechanical stability, and strong shear resistance.

Description

Technical Field

[0001] The invention relates to the technical field of chemical materials, and more specifically to a preparation method of a highly resistant circulating water-based aluminum pigment, and the prepared highly resistant circulating water-based aluminum pigment and application thereof. Background Art

[0002] Aluminum pigment is a flaky particle with a specific particle size that is made by grinding and mixing micron-sized spherical aluminum powder using a dry or wet process. It has good metallic luster and metallic texture and is widely used in coatings, plastics, ceramics, printing inks and other fields. With the improvement of environmental protection requirements, the research and development of aluminum pigments has also shifted from solvent-based to water-based, and the application and development of corresponding water-based aluminum pigments have become popular in recent years. The application of water-based aluminum pigments in coatings is mainly used as water-based system coatings such as automotive paints, automotive repair paints, automotive parts, plastic coatings, coil paints, and building exterior walls.

[0003] In the field of automotive paint, in the automatic spraying process of the automotive industry, aluminum pigments are exposed to high shear stress and can easily react with water in the paint to turn black or produce hydrogen. Therefore, aluminum pigments require ultra-high mechanical stability. At present, the commonly used water-based aluminum pigments for automobiles on the market are Hydrolan series aluminum pigments produced by Eckart of Germany, EMR series aluminum pigments of Toyo, and SILBERCOTE series aluminum pigments of Starlink. At present, the general water-based aluminum pigments for original automotive paints are mainly coated with silica, but after enhanced cyclic shear tests, aluminum pigments mainly coated with silica have poor cyclic resistance and cannot meet the performance requirements of the coatings industry. Summary of the invention

[0004] In view of the shortcomings of the prior art, one of the purposes of the present invention is to provide a highly cyclically resistant water-based aluminum pigment to improve the cyclic resistance of the aluminum pigment.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A highly resistant circulating water-based aluminum pigment comprises the following steps:

[0007] (1) adding a silver dollar type aluminum pigment slurry to a double-jacketed reactor equipped with a thermostat, a reflux condenser and a stirrer, dispersing the slurry with isopropanol, and stirring the dispersion system to obtain an aluminum pigment suspension; wherein the silver dollar type aluminum pigment slurry is added first and then the isopropanol is added to avoid splashing of the isopropanol liquid;

[0008] (2) dissolving polyvinyl butyral in water, and adding a surfactant thereto to prepare a polymer solution;

[0009] (3) adding the aluminum pigment suspension dispersed in step (1) into a reaction kettle containing a polymer solution, stirring and coating, centrifuging, washing, and drying to obtain aluminum-polyvinyl butyral;

[0010] (4) Adding a silane coupling agent to the system of step (3), heating the reaction system, and then adding oxalic acid to adjust the pH of the system to 4-5, stirring for a while, and then dropping monoethanolamine diluted with isopropanol into the reaction system, and continuing to stir for a while;

[0011] (5) The silane coupling agent diluted with isopropanol is added dropwise to the reaction system, and the mixture is further stirred for a period of time. The reaction mixture is cooled, and the color paste is separated by filtering through a funnel to remove the filter cake, thereby finally obtaining a highly resistant circulating water-based aluminum pigment.

[0012] The present invention adopts a double-layer coating system, in which the inner layer is coated with a flexible organic polymer such as polyvinyl butyral to coat the aluminum pigment core, and the outer layer is coated with a rigid silane coupling agent. The inner layer provides buffering and the outer layer enhances protection. The two work synergistically, and the prepared pigment has high outgassing stability and mechanical stability, and strong shear resistance.

[0013] Preferably, in step (1), the weight ratio of the silver dollar aluminum pigment slurry to isopropanol is 1:1-1:1.5; and the dispersion system is stirred for 30-40 minutes.

[0014] Preferably, in step (2), the degree of polymerization of the polyvinyl butyral is between 500 and 2000; the surfactant is hexadecyltrimethylammonium chloride, sodium dodecylbenzene sulfonate, long-chain sulfonic polyethylene glycol or sodium polyepoxysuccinate; the amount of the polyvinyl butyral is 10-40% of the silver dollar type aluminum pigment paste, and the amount of the surfactant is 0.1-0.2% of the silver dollar type aluminum pigment paste.

[0015] Preferably, in step (3), the stirring and coating temperature is 20-25°C, the stirring and coating time is 30-120min, and the stirring and coating speed is 200-300r / min; the washing method is to wash once with deionized water and then wash twice with anhydrous ethanol.

[0016] Preferably, step (4) is specifically as follows: first, a silane coupling agent is added dropwise to the reaction system of step (3), the reaction system is heated to 60-80° C., oxalic acid is added to adjust the pH of the system to 4-5, the mixture is stirred for 120-160 min, and then monoethanolamine diluted with isopropanol is added dropwise to the reaction system within 3 h, and stirring is continued for 5-8 h.

[0017] Preferably, in step (4), the silane coupling agent is one or a mixture of tetraethoxysilane, aminopropyltriethoxysilane, glycidyloxypropyltrimethoxysilane, and phenyltriethoxysilane; and the amount of the silane coupling agent used is 20-25% of the silver dollar type aluminum pigment slurry.

[0018] Preferably, in step (5), the silane coupling agent is one or a mixture of tetraethoxysilane, aminopropyltriethoxysilane, glycidyloxypropyltrimethoxysilane, and phenyltriethoxysilane; and the amount of the silane coupling agent used is 20-25% of the silver dollar type aluminum pigment slurry.

[0019] Preferably, in step (5), the further stirring time is 300-350 min; and the reaction mixture is cooled to 40°C.

[0020] The second object of the present invention is to provide a highly resistant to circulating water-based aluminum pigment, which is prepared using the above-mentioned method for preparing the highly resistant to circulating water-based aluminum pigment.

[0021] A third object of the present invention is to provide an application of the above-mentioned highly resistant circulating water-based aluminum pigment in automatic spraying water-based automobile coatings.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention adopts a double-layer coating system, in which the inner layer is coated with a flexible organic polymer such as polyvinyl butyral to coat the aluminum pigment core, and the outer layer is coated with a rigid silane coupling agent. The inner layer provides buffering and the outer layer enhances protection. The two work synergistically, and the prepared pigment has high outgassing stability and mechanical stability, and strong shear resistance. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] In the following embodiments:

[0026] The silver dollar aluminum pigment paste is selected from the water-based aluminum silver paste model WHD6613A produced by Hefei Xuyang Aluminum Pigment Co., Ltd.

[0027] Hydrolan 2156 pigment is 2156 Silver water-based / solvent-based silver paste from Eckart, Germany.

[0028] The milky white / colorless hybrid varnish is ZW42-6008-0101 from BASF Coatings.

[0029] The colorless binder is ZK266826 polyester resin from BASF Coatings.

[0030] Unless otherwise specified, the experimental materials and reagents used in the following examples can be obtained from commercial channels. If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0031] Example 1

[0032] This embodiment provides a method for preparing a highly resistant circulating water-based aluminum pigment, comprising the following steps:

[0033] (1) Add 123 g of silver dollar aluminum pigment slurry into a 1 L double-jacketed reactor equipped with a thermostat, a reflux condenser and a stirrer, disperse it with 150 g of isopropanol, and stir the dispersion system for 30 min to obtain an aluminum pigment suspension;

[0034] (2) taking 1 kg of deionized water, adding 0.24 g of long-chain sulfonic polyethylene glycol and 15 g of polyvinyl butyral with a degree of polymerization of 1800 to prepare a polymer solution;

[0035] (3) adding the aluminum pigment suspension dispersed in step (1) to a reactor containing a polymer solution, stirring and reacting at a temperature of 25° C. and a speed of 200 r / min for 60 min, centrifuging, washing once with 1 L of deionized water, then washing twice with 1 L of anhydrous ethanol, and then drying in a vacuum drying oven to obtain aluminum-polyvinyl butyral;

[0036] (4) 25.5 g of tetraethoxysilane, 3 g of aminopropyl triethoxysilane and 1 g of glycidyloxypropyl trimethoxysilane were added dropwise to the system of step (3) in batches, and after heating to 60° C., oxalic acid was added to adjust the pH of the system to 4-5, and the mixture was stirred for 160 min. Then, monoethanolamine diluted with isopropanol was added dropwise to the reaction system within 3 h, and stirring was continued for 8 h.

[0037] (5) 20 g of tetraethoxysilane, 5 g of phenyltriethoxysilane and 1 g of aminopropyltriethoxysilane diluted with isopropanol were added dropwise to the reaction system in batches, and the mixture was further stirred for 350 min. The reaction mixture was cooled to 40° C., and the color paste was separated by filtering through a funnel to remove the filter cake, thereby finally obtaining a highly resistant circulating water-based aluminum pigment with an aluminum content of 60%.

[0038] Example 2

[0039] This embodiment provides a method for preparing a highly resistant circulating water-based aluminum pigment, comprising the following steps:

[0040] (1) Add 123 g of silver dollar aluminum pigment slurry into a 1 L double-jacketed reactor equipped with a thermostat, a reflux condenser and a stirrer, disperse it with 150 g of isopropanol, and stir the dispersion system for 30 min to obtain an aluminum pigment suspension;

[0041] (2) taking 1 kg of deionized water, adding 0.24 g of long-chain sulfonic polyethylene glycol and 25 g of polyvinyl butyral with a degree of polymerization of 1700 to prepare a polymer solution;

[0042] (3) adding the aluminum pigment suspension dispersed in step (1) to a reactor containing a polymer solution, stirring and reacting at a temperature of 25° C. and a speed of 200 r / min for 90 min, centrifuging, washing once with 1 L of deionized water, then washing twice with 1 L of anhydrous ethanol, and then drying in a vacuum drying oven to obtain aluminum-polyvinyl butyral;

[0043] (4) 25.5 g of tetraethoxysilane, 3 g of aminopropyl triethoxysilane and 1 g of glycidyloxypropyl trimethoxysilane were added dropwise to the system of step (3) in batches, and after heating to 60° C., oxalic acid was added to adjust the pH of the system to 4-5, and the mixture was stirred for 160 min. Then, monoethanolamine diluted with isopropanol was added dropwise to the reaction system within 3 h, and stirring was continued for 8 h.

[0044] (5) 20 g of tetraethoxysilane, 5 g of phenyltriethoxysilane, and 1 g of aminopropyltriethoxysilane diluted with isopropanol were added dropwise to the reaction system and further stirred for 350 min. The reaction mixture was cooled to 40° C. and the color paste was separated by filtering through a funnel to remove the filter cake, thereby finally obtaining a highly resistant circulating water-based aluminum pigment.

[0045] Example 3

[0046] This embodiment provides a method for preparing a highly resistant circulating water-based aluminum pigment, comprising the following steps:

[0047] (1) Add 123 g of silver dollar aluminum pigment slurry into a 1 L double-jacketed reactor equipped with a thermostat, a reflux condenser and a stirrer, disperse it with 150 g of isopropanol, and stir the dispersion system for 30 min to obtain an aluminum pigment suspension;

[0048] (2) taking 1 kg of deionized water, adding 0.24 g of long-chain sulfonic polyethylene glycol and 35 g of polyvinyl butyral with a degree of polymerization of 1800 to prepare a polymer solution;

[0049] (3) adding the aluminum pigment suspension dispersed in step (1) to a reactor containing a polymer solution, stirring and reacting at a temperature of 25° C. and a speed of 200 r / min for 120 min, centrifuging, washing once with 1 L of deionized water, then washing twice with 1 L of anhydrous ethanol, and then drying in a vacuum drying oven to obtain aluminum-polyvinyl butyral;

[0050] (4) 25.5 g of tetraethoxysilane, 3 g of aminopropyl triethoxysilane and 1 g of glycidyloxypropyl trimethoxysilane were added dropwise to the system of step (3) in batches, and after heating to 60° C., oxalic acid was added to adjust the pH of the system to 4-5, and the mixture was stirred for 160 min. Then, monoethanolamine diluted with isopropanol was added dropwise to the reaction system within 3 h, and stirring was continued for 8 h.

[0051] (5) 20 g of tetraethoxysilane, 5 g of phenyltriethoxysilane, and 1 g of aminopropyltriethoxysilane diluted with isopropanol were added dropwise to the reaction system and further stirred for 350 min. The reaction mixture was cooled to 40° C. and the color paste was separated by filtering through a funnel to remove the filter cake, thereby finally obtaining a highly resistant circulating water-based aluminum pigment.

[0052] Example 4

[0053] This embodiment provides a method for preparing a highly resistant circulating water-based aluminum pigment, comprising the following steps:

[0054] (1) Add 123 g of silver dollar aluminum pigment slurry into a 1 L double-jacketed reactor equipped with a thermostat, a reflux condenser and a stirrer, disperse it with 150 g of isopropanol, and stir the dispersion system for 30 min to obtain an aluminum pigment suspension;

[0055] (2) taking 1 kg of deionized water, adding 0.24 g of long-chain sulfonic polyethylene glycol and 45 g of polyvinyl butyral with a degree of polymerization of 1800 to prepare a polymer solution;

[0056] (3) adding the aluminum pigment suspension dispersed in step (1) to a reactor containing a polymer solution, stirring and reacting at a temperature of 25° C. and a speed of 200 r / min for 30 min, centrifuging, washing once with 1 L of deionized water, then washing twice with 1 L of anhydrous ethanol, and then drying in a vacuum drying oven to obtain aluminum-polyvinyl butyral;

[0057] (4) 25.5 g of tetraethoxysilane, 3 g of aminopropyl triethoxysilane and 1 g of glycidyloxypropyl trimethoxysilane were added dropwise to the system of step (3) in batches, and after heating to 60° C., oxalic acid was added to adjust the pH of the system to 4-5, and the mixture was stirred for 160 min. Then, monoethanolamine diluted with isopropanol was added dropwise to the reaction system within 3 h, and stirring was continued for 8 h.

[0058] (5) 20 g of tetraethoxysilane, 5 g of phenyltriethoxysilane, and 1 g of aminopropyltriethoxysilane diluted with isopropanol were added dropwise to the reaction system and further stirred for 350 min. The reaction mixture was cooled to 40° C. and the color paste was separated by filtering through a funnel to remove the filter cake, thereby finally obtaining a highly resistant circulating water-based aluminum pigment.

[0059] Cycle resistance test

[0060] The cycle resistance performance of the sample in Example 1 and the comparative example sample was compared.

[0061] The sample of Example 1 is a highly resistant circulating water-based aluminum pigment having an aluminum content of 60%.

[0062] The comparative example sample is an aluminum pigment of the commercially available model number Hydrolan 2156.

[0063] Specific detection method: Pre-disperse 2.5% aluminum pigment in 3% ethylene glycol butyl ether, stirring time is 5 minutes; mix the suspension with 2.5% colorless adhesive, stir for 55 minutes, stir the suspension, add 87% milky white / colorless mixed varnish, 10% nano iron oxide red to test the effect. After the above coating system is configured, the pH is finally adjusted to 9.0 with 10wt.% dimethylethanolamine solution (solvent water). The coating configured according to the above ratio is subjected to enhanced pipeline circulation test, and the degassing test is performed by sampling different number of cycles. After the circulating pipeline test, the comparative sample fails after 1 hour of circulation, and 19ml of gas is released in one day. The sample of Example 1 fails after 6 hours of circulation, and 17ml of gas is released in two days.

[0064] 1. Comparison of the test data of the two groups of products, the results are shown in Table 1.

[0065] Table 1 Comparison of test results before and after the cycle of the samples of Example 1 and the comparative example

[0066]

[0067] 2. Initial deflation

[0068] Take 280g of the pH = 9.0 coating prepared according to the above ratio and introduce it into a gas flask sealed with a new gas collection device (publication (announcement) number: CN213913863U). The gas washing bottle is placed in a 40℃ water bath for 1 hour, hermetically sealed, and tested for 30 days. The volume of gas produced is read based on the displacement of the upper chamber of the bubble counter. After 30 days, if a maximum of 10ml of hydrogen is precipitated, the test is considered to have passed. If the sample is unstable throughout the period, the time before the sample is deflated is recorded.

[0069] Table 2 Outgassing test results of Example 1 samples and comparative samples (before circulation)

[0070]

[0071] 3. Optical test results (before cycling)

[0072] Table 3 Optical test results of samples of Example 1 and comparative examples (before cycling)

[0073]

[0074] Note: Among them, L * Indicates the brightness at different angles, used to describe the brightness of the color; △L * It represents the brightness difference between two color samples at different angles; Sa represents the average surface roughness at different angles; △Sa represents the change in average surface roughness; G represents glossiness; △G represents the change in glossiness.

[0075] 4. Moisture and heat resistance

[0076] Under the conditions of 50°C, 98%RH, and 240h, the high circulating water-resistant aluminum pigment with an aluminum content of 60% prepared in Example 1 of the present invention and the aluminum pigment of the comparative example both have a blistering grade of 0, a discoloration grade of 0, a gloss loss grade of 0, a rust grade of 0, and an adhesion of 0; therefore, the high circulating water-resistant aluminum pigment with an aluminum content of 60% prepared in Example 1 of the present invention and the aluminum pigment of the comparative example both have qualified moisture and heat resistance.

[0077] 5. Pipeline circulation deflation

[0078] The results of the pipeline circulation degassing test are shown in Tables 4 and 5. It can be seen that the high circulation resistance water-based aluminum pigment prepared in Example 1 of the present invention has a hydrogen evolution gas emission of only 7.0 ml after 5 hours of circulation and 30 days, which is within the qualified range; while the aluminum pigment sample of the comparative example has a hydrogen evolution gas emission of 19.0 ml after 1 hour of circulation and 1 day, which exceeds the qualified range.

[0079] Table 4 Pipeline cycle degassing test results of samples in Example 1

[0080]

[0081] Table 5 Pipeline cycle degassing test results of comparative samples

[0082]

[0083] 6. Optical test results (after cycling)

[0084] The lack of optical test results of the comparative sample in Table 6 is because the gas test after shearing did not pass in a very short period of time, so further optical testing was stopped. However, after the circulation pipeline was operated for 5 hours, the sample of Example 1 still had a stable ΔL* value on the basis of ensuring qualified degassing.

[0085] Table 6 Optical test results (after 5 hours of circulation)

[0086]

[0087] The present invention adopts a double-layer coating system, in which the inner layer is coated with a flexible organic polymer such as polyvinyl butyral to coat the aluminum pigment core, and the outer layer is coated with a rigid silane coupling agent. The inner layer provides buffering and the outer layer enhances protection. The two work synergistically, and the prepared pigment has high outgassing stability and mechanical stability, and strong shear resistance.

[0088] The embodiments of the present invention disclose preferred embodiments, but are not limited thereto. A person skilled in the art can easily understand the spirit of the present invention based on the above embodiments and make different extensions and changes. However, as long as they do not deviate from the spirit of the present invention, they are all within the protection scope of the present invention.

Claims

1. A method for preparing a highly resistant circulating water-based aluminum pigment, characterized in that: The following steps are involved: (1) adding a silver dollar type aluminum pigment slurry into a double-jacketed reactor equipped with a thermostat, a reflux condenser and a stirrer, dispersing the slurry with isopropanol, and stirring the dispersion system to obtain an aluminum pigment suspension; (2) dissolving polyvinyl butyral in water, and adding a surfactant thereto to prepare a polymer solution; (3) adding the aluminum pigment suspension dispersed in step (1) to a reaction kettle containing a polymer solution, stirring for coating, centrifuging, washing, and drying to obtain aluminum-polyvinyl butyral; (4) adding a silane coupling agent to the system of step (3), heating the reaction system, adding oxalic acid to adjust the pH of the system to 4-5, stirring for a while, and then dropping monoethanolamine diluted with isopropanol into the reaction system, and continuing to stir for a while; (5) adding the silane coupling agent diluted with isopropanol dropwise to the reaction system, further stirring for a period of time, cooling the reaction mixture, filtering the color paste through a funnel to remove the filter cake, and finally obtaining a highly resistant circulating water-based aluminum pigment; In step (1), The weight ratio of the silver dollar aluminum pigment slurry to isopropyl alcohol is 1:1-1:1.5; Stir the dispersed system for 30-40 minutes; In step (2), The degree of polymerization of the polyvinyl butyral is between 500 and 2000; The surfactant is hexadecyltrimethylammonium chloride, sodium dodecylbenzenesulfonate, long-chain sulfonic acid polyethylene glycol or sodium polyepoxysuccinate; The dosage of the polyvinyl butyral is 10-40% of the silver dollar type aluminum pigment slurry, and the dosage of the surfactant is 0.1-0.2% of the silver dollar type aluminum pigment slurry.

2. The method for preparing a highly resistant circulating water-based aluminum pigment according to claim 1, characterized in that: In step (3), The stirring and coating temperature is 20-25°C, the stirring and coating time is 30-120min, and the stirring and coating speed is 200-300r / min; The washing method comprises washing once with deionized water and then washing twice with anhydrous ethanol.

3. The method for preparing the highly resistant circulating water-based aluminum pigment according to claim 1, characterized in that: Step (4) is specifically as follows: first, a silane coupling agent is added dropwise to the reaction system of step (3), the reaction system is heated to 60-80° C., oxalic acid is added to adjust the pH of the system to 4-5, the mixture is stirred for 120-160 min, and then monoethanolamine diluted with isopropanol is added dropwise to the reaction system within 3 h, and stirring is continued for 5-8 h.

4. The method for preparing the highly resistant circulating water-based aluminum pigment according to claim 3, characterized in that: In step (4), The silane coupling agent is one or a mixture of tetraethoxysilane, aminopropyltriethoxysilane, glycidyloxypropyltrimethoxysilane, and phenyltriethoxysilane; The dosage of the silane coupling agent is 20-25% of the silver dollar type aluminum pigment slurry.

5. The method for preparing the highly resistant circulating water-based aluminum pigment according to claim 1, characterized in that: In step (5), The silane coupling agent is one or a mixture of tetraethoxysilane, aminopropyltriethoxysilane, glycidyloxypropyltrimethoxysilane, and phenyltriethoxysilane; The dosage of the silane coupling agent is 20-25% of the silver dollar type aluminum pigment slurry.

6. The method for preparing the highly resistant circulating water-based aluminum pigment according to claim 1, characterized in that: In step (5), The further stirring time is 300-350min; The reaction mixture was cooled to 40 °C.

7. A highly resistant to circulating water-based aluminum pigment, prepared using the method for preparing the highly resistant to circulating water-based aluminum pigment according to any one of claims 1 to 6.

8. Use of the highly circulating water-based aluminum pigment as claimed in claim 7 in automatic spraying water-based automobile coatings.

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